Control equipment for prime mover driven synchronous generators



Oct. 26, 1943. H. BANY 2,332,836

CONTROL EQUIPMENT FOR PRIME MOVER DRIVEN SYNCHRONOUS GENERATORS FiledDec. 24, 1942 Inventor: Herman Bang;

WW T/JW by His Attorrweg.

Patented Oct. 26, ki ls;

CONTROL EQUIPMENT FOR PRIME MOVER DRIVEN SYNCHRONOUS GENERATORS HermanBany, Lansdowne, Pa., assignor to General Electric Company, acorporation of New York Application December 24, 1942, Serial No.469,989

9 Claims.

My invention relates to control equipments for prime mover drivensynchronous generators and particularly to an equipment for controllingthe operation of such a generator when it falls out of step, and theobject of my invention is to provide an improved arrangement ofapparatus for restoring synchronous operation of such a generator asquickly as possible after it falls out of step.

My invention will be better understood from the following descriptionwhen taken in connection with the accompanying drawing, the singlefigure of which diagrammatically illustrates a control equipment for aprime mover driven synchronous generator embodying my invention, and itsscope will be pointed out in the appended claims.

Referring to the drawing, I represents a synchronous generator driven bya suitable prime mover 2. The supply of driving energy to the primemover 2 is controlled by a gate 3, the position of which is controlledby a suitable governor 4 which, as shown, includes the fly balls 9 givenby the prime mover 2 and arranged to con trol the position of a movablemember 6, which in turn controls the position of the gate 3. As shown,the movable member 6 is in the gateclosed position and is held in thatposition by a closing spring I against the bias of an opening spring 8as long as a governor magnet 9 is deenergized. When the magnet 9 isenergized, it moves the closing spring I out of operative relation withthe movable member I; and allows the opening spring 8 to move themovable member 6 to an opening position determined by the position ofthe fly balls 5.

The generator I is arranged to be connected to an energized alternatingcurrent system Ill by a circuit breaker I I which may be of any suitabletype. In order to simplify the disclosure, I have shown the circuitbreaker II as being of the manually controlled type, but it will beobvious that it may be automatically controlled in any suitable manner.

The generator I is provided with a field winding I3 which is arranged tobe short-circuited through a suitable discharge resistor I4 in oneposition of a two-position field switch I and to a suitable source ofexcitation I6 when the field switch I5 is in its other position.

The prime mover 2 is arranged to be started and stopped in response tothe closing and opening of a control switch II. While I have shown thecontrol switch H as being manually controlled, it will be obvious thatit may be automatically controlled in various ways, examples of whichare well known in the art. The closing of the control switch I1, wheneither the circuit breaker II or the field switch I5 is open, effectsthe energization of a control relay l8, which in turn effects theenergization of another control relay I9 to complete an energizingcircuit for the closing coil 20 of the field switch I5 so as to connectthe generator field winding l3 to the source of excitation I6. Theclosing of the field switch I5 also completes an energizing circuit forthe governor magnet 9 so as to render the governor 4 operative to startthe prime mover 2 from rest and bring it up to th normal operating speedwhen the circuit breaker II is closed to synchronize the generator Iwith the electric system I0. The closing of the circuit breaker II andthe field switch I5 changes the connection of the closing coil 20 of thefield switch I5 so that thereafter the energization of the closing coil20 depends upon the position .of the contacts 22 01' an out-of-stepresponsive relay 23, which is so connected that the contacts 22 areopened whenever the generator i pulls out of step. United States Patent2,151,160, granted March 21, 1939, on an application filed by Harold T.Seeley and assigned to the same assignee as this application, disclosesan impedance responsive relay which when designed with the properoperating characteristics for use with a generator is particularlyadapted for use as an out-of-step responsive relay in the embodiment ofmy invention shown in the drawing since it responds, just prior toactual pull out, to a predetermined armature circuit of the generatorindicative that the generator is about to pull out of step. Such animpedance relay comprises a rotatable member 24 and a cooperatingwattmetric driving element 25 that includes a current winding 26energized in response to the current in one of the phase conductorsconnected to the armature winding of the generator 5 and a voltagewinding 21 connected in series relation with a capacitor 28 and aresistor 29 across one phase of the armature winding of the generator I.The rotatable member 24, which controls the opening and closing of thecontacts 22, is also provided with another driving element 30 which hasa voltage winding 3| connected across one phase of the armature circuitof the generator I with a resistor 32 and a capacitor 33 in seriestherewith. This driving element 30 exerts a torque on the rotatableelement 24 in a direction to close the contacts 22. When the fieldswitch I5 is closed, the auxiliary contacts 34 thereof shunt thecapacitor 28 and the resistor 33 in the circuit of the voltage winding3| so that the operating characteristic of the relay 23 is such that thecontacts 22 are closed for a sufficient length of time to efiect theoperation of the time relay I9 only when the slip of the generator I isI below a predetermined value.

In accordance with my invention, the opening of the contacts 22 of theout-of-step responsive relay 23, when the generator pulls out of step,efiects the opening of the field switch I and the deenergization of thegovernor magnet 9 so as to decrease the supply of driving energy to theprime mover 2. When the speed of the out-of-step generator decreasessufficiently so that the slip of the generator is less than apredetermined value, the relay 23 is arranged to maintain its contacts22 closed for a suflicient length of time to pick up the time relay I9and thereby effect the closing of the field switch I5 to pull thegenerator into synchronism with the system III. The closing of the fieldswitch I5 also reenergizes thegovernor magnet 9 so that the amount ofdriving energy supplied to the prime mover is increased sufficiently toplace the prime mover 2 again under th control of the governor 4.

The operation of the arrangement shown in the drawing is as follows:When the prime mover driven generator I is shut down, thevarious controldevices are in the positions in which they are shown in the drawing.When it is desired to place the generator I in operation, the controlswitch I1 is closed so as to complete through the parallel-connectedcontacts 40 on the circuit breaker II and the contacts 4| on the fieldswitch I5 an energizing circuit for the control relay I8. The closing ofthe contacts 42 of the control relay I8 completes through the contact ofthe control switch II, the contacts 43 of the control relay 44, and theauxiliary contacts 45 on the field switch I5 an energizing circuit forthe time relay I9. After being energized for a predetermined time, therelay I9 closes its contacts 45 and completes through the contacts ofthe control switch II, the contacts 42 of the control relay I8, and thecontacts 43 of the control relay 44 an energizing circuit for theclosing coil 20 so that the field switch I5 is closed to connect thefield winding I3 of the generator I to the source of excitation I5. Theclosing of the auxiliary contacts 41 and 48 on the field switch I5completes shunt circuits around the contacts 45 of the relay I9 and thecontact 43 of the relay 44, respectively, in the energizing circuit ofthe closing coil 20. The closing of the auxiliary contacts 49 on thefield switch I5 completes through i the contacts of the control switchI! an energizmover 2 and the generator I at the desired operating speed.The circuit breaker II is then closed in any suitable manner to effectthe synchronization of the generator I with the system II).

The closing of the auxiliary contact 5| on the circuit breaker IIcompletes an energizing circuit for the control relay 44, and theopening of the auxiliary contacts 40 on the circuit breaker IIinterrupts the energizing circuit of the control relay I8 which, afterbeing deenergized for a predetermined time, opens the energizing circuitof the closing coil 29 of the field switch I5. However, before the relayI8 opens its contacts 42, the generator pulls into synchronism and therelay 23 operates to close its contacts 22 to complete another holdingcircuit for the closing coil 20 of the field switch I5 through thcontacts of the control switch I1 and the auxiliary contacts 41 on thefield switch I5. Therefore, as long as the generator I continues tooperate in synchronism, the field switch I5 remain closed and the speedof the prime mover 2 is maintained at the desired value by the operationof the governor 4.

When, however, the generator I starts to fall out of synchronism, thepower factor thereof changes to such a leading value prior to thegenerator actually falling out of step, as to cause the out-of-steprelay 23 to open immediately its contacts 22 and effect thedeenergization of the closing coil 20 of the field switch so that thefield winding I3 is disconnected from the source of excitation I6 andthe discharge resistor I4 is connected across the terminals of the fieldwinding I3, thereby causing the generator to operate as an inductiongenerator driven by the prime mover 2. The opening of the auxiliarycontacts 49 on the field switch. I5 deenergize the governor magnet 9 sothat the closing spring I is 0D- erative to move the movable member '5of the governor 4 toward its closed position thereby effecting theclosing of the gate 5 and a decrease in the speed of the generator I soas to restore it back toward its normal no-load speed. The

closing of the contacts M on the field switch I5 completes theenergizing circuit of the control relay I8 in the manner heretoforedescribed, but the closing of the contacts 42 of the relay I9 at thistime does not complete an energizing circuit for the closing coil 20because this energizing circuit is now open at the contacts 43 of thecontrol relay 44. The opening of the auxiliary contacts 34 and theclosing of the auxiliary contacts 50 on the field switch I5, when it isopened, change the connections of the windings 21 and 3| of theout-of-step relay 23 so that when the slip of the generator I decreasesbelow a predetermined value, the contacts 22 remain closed for asufiicient length of time during each slip cycle to maintain the circuitof the time relay I9 energized through the auxiliary contacts 45 on thefield switch I5 and the contacts of the control relay I8 long enough tocause the relay I9 to closeits contacts 45 and complete the heretoforedescribed energizing circuit for the closing coil 20. The closing of thefield switch I5 then effects in a manner heretofore described theresynchronization of the generator I and the reenergization of thegovernor magnet 9 so as to restore normal operation of the prime moverdriven generator I.

While I have, in accordance with the patent statutes, shown anddescribed my invention as applied to a particular system and asembodying tor and for shutting oiI the supply of driving energy to saidprime mover while maintaining said generator connected to thealternating current system, and means responsive to a predeterminedarmature circuit condition of said generator while it is connected tosaid system with its excitation removed for restoring excitation to saidgenerator and for increasing the supply of driving energy to said primemover.

2. In combination, a synchronous generator connected to an alternatingcurrent system, a

prime mover driving said generator, means forshutting off the supplyof-driving energy to said prime mover, means responsive to anout-of-step condition of said generator for removing excitation fromsaid generator and for initiating said shutting ofl. means whilemaintaining said gen erator connected to the alternating current system,and means responsive to a predetermined armature circuit condition ofsaid generator while it is connected to said system with its excitationremoved for restoring excitation to said generator and for renderingsaid shutting oil? means inoperative to shut ofl the supply of drivingenergy to said prime mover.

3. In combination, a synchronous generator connected to an alternatingcurrent system, a

prime mover driving said generator, means responsive to an out-of-stepcondition of said generator for removing excitation from said generatorand for shutting oi! the .supply of driving energy to said prime moverwhile maintaining said generator connected to the alternating currentsystem, and means responsive to the slip of said generator decreasingbelow a predetermined value for restoring excitation to said generatorand for increasing the supply of driving energy to said prime mover.

4. In combination, a synchronousgenerator connected to an alternatingcurrent system, a prime mover driving said generator, means for shuttingoff the supply oi! driving energy to said prime mover, a source ofexcitation, a field switch connecting said source to the field windingoi said generator, means responsive to an out-of-step condition of saidgenerator for effecting the opening of said field switch and theinitiation of the operation of said shutting oil means, and meansresponsive to the slip of said generator decreasing below apredetermined value for reclosing said field switch and rendering saidshutting oi! connecting said source to the field winding of saidgenerator, means responsive to an out-ofstep condition of said generatorfor eil'ecting the opening of said field switch, and means respon siveto the opening of said switch for initiating ,the operation of saidshutting off means.

means inoperative to shut oil. the supply of driv- 6. In combination, asynchronous generator connected to an alternating current system, aprime mover driving said generator, means for shutting oil the supply ofdriving energy to said prime mover, a source of excitation, a fieldswitch connecting said source to the field winding of said generator,meansresponsive to an out-ofstep condition of aid generator foreffecting the opening of said field switch, means responsive to theopening of said switch for initiating the operation of said shutting offmeans, and means responsive to theislip of said generator decreasingbelow a predetermined value for reclosing said field switch andrendering said shutting off means inoperative to shut off the supply ofdriving energy to said prime mover,

"7. In combination, a synchronous generator connected to an alternatingcurrent system, a prime mover driving said generator, means responsiveto a predetermined armature circuit condition of said generatorindicative that said generator is about to fall out of step for removingexcitation from said generator and for shutting off the supply ofdriving energy to said prime mover while maintaining said generatorconnected to the alternating current system, and means responsive to apredetermined armature circuit condition of said generator while it isconnected to said system with its excitation removed for restoringexcitation to said generator and for increasing the supply of drivingenergy to said prime mover.

8. In combination, an alternating current circuit, a synchronousimachinehaving an armature winding and a field winding, a circuit breaker forconnecting the armature winding of said machine to said circuit, asource of excitation, a field switch for connecting said source to thefield winding of said machine, means for closing said field switch whilesaid circuit breaker is open, means for opening said field switch whilesaid circuitbreaker remains closed, and means dependent upon apredetermined speed condition or said machine for reclosing said fieldswitch while saidcircuit breaker is closed.

9. In combination, an altemating current circult, a synchronous machinehaving an armature winding and a field winding, a circuit breakerconnecting said armature winding to said circuit, a source ofexcitation, a field switch connecting said source to said field winding,a control switch, means responsive to a predetermined electric conditionof said machine for effecting the opening of said field switch whilesaid circuit breaker remains closed, means'dependent upon apredetermined speed condition of said machine for reclosing said fieldswitch while said circuit breaker is closed and said control switch isin a predetermined position, and means for closing said field switchindependently or said predetermined speed condition when said circuitbreaker is open and said control switch is in said predeterminedposition.

HERMAN .BANY.

